The enhanced electronic transference number at the grain boundaries in Sr-doped LaGaO3

The partial electron-hole conductivity of the bulk and the grain boundary of 1 mol% Sr-doped LaGaO3 has been measured separately using a dc-polarization method employing an oxygen ion-blocking cell. The electronic transference number for the electron-hole at the grain boundary was found to be greater than that in the bulk. This is because the oxygen vacancy depletes more severely in the grain boundary area than the electron-hole does to form the space charge zone, due to its higher effective charge compared to that of the electron-hole. Such a local variation in the electronic transfer number thus confirms that the conduction across the grain boundary in 1 mol% Sr-doped LaGaO3 is controlled by the space charge. These results are consistent with those previously reported based on the ac impedance studies.